One known form of braided product is the Expando.TM. self-fitting protective oversleeve made by Bentley-Harris Manufacturing Co. of Lionville, Pa. This tubular sleeve is expandable in that, when the ends are pushed toward each other it expands in diameter, and when they are released it returns to its original shape and size. This enables it to be pulled or pushed over objects of different diameters, including diameters greater than the unstressed or "rest" diameter of the sleeve, and also enables it to accommodate expansion, bending and twisting of hoses or wires which may run through it. This expandable braided product also exhibits a "spring-back" or "memory" characteristic, whereby it tends to return to its rest diameter when released from longitudinal forces. Such expandable braided sleeving has been widely used, for example to protect, and/or dress, wiring harnesses and hose assemblies.
One difficulty with the typical braided product of the expandable type is that when the braid is cut in an ordinary manner, as by scissors, the ends of the braid will tend to unravel or splay, the braiding coming apart for a substantial distance back from the cut ends. This is particularly troublesome when an end of a braided sleeve must be forced over a large-diameter object, causing the monofilaments to splay and therefore no longer provide the desired type of tight fit on the samller-diameter contents of the tubular covering; in addition, such splaying is cosmetically very undesirable.
There are currently three principal ways in which this problem has been addressed, as follows:
(1) Coat the braided product with a continuous coating. This eliminates the splaying, but also restricts the expandability of the braid and therefore its ability to slide over, or wrap around, an object with full conformity to a variable cross-section of the object. Such a construction also prevents one from "breaking out" a branching wire from the interior of braided tubing, as is sometimes desirable.
(2) Heat-set the braided product. Heating the completed product will put a slight set into the braid, but with even slight mechanical expansion the ends will unbraid and splay out again.
(3) Cut the braid with a hot knife or wire. With most plastic braidings, the sleeve can be cut through with a hot knife or wire, thereby fusing the monofilaments to each other to prevent the braid from fraying or unraveling. However, such end treatment will fix the diameter at that set by the fusing of the end of the tubular braid, and thereby prevent the braid from expanding readily to receive a large object. Further, this method requires use of special hot melt devices to provide such cutting of the braid, and therefore is not useful for field installations of the sleeve where no such special tools are available.
Accordingly, it is an object of the present invention to provide a new braided product and method of making it, which minimize such fraying while retaining the natural expansion and contraction characteristics of the expandable type of braided product.
It is also an object of the invention to provide such method and apparatus in which the treatment providing the above described advantageous characteristics is readily and inexpensively performed, and in which the user can cut the resultant braided product to the desired length without having to use any special cutting or bonding tools.